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Antioxidants, nature and chemistry
Submitted by
Dr. Tamer Fouad, M.D.
Classification of major antioxidants
Table 2 Classification of major antioxidants
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Enzymes
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Antioxidant
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Role
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Remarks
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Superoxide dismutase (SOD)
Mitochondrial
Cytoplasmic
Extracellular
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Dismutates O2·⁻
to H2O2
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Contains Manganese (Mn.SOD)
Contains Copper & Zinc (CuZnSOD)
Contains Copper (CuSOD)
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Catalase
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Dismutates H2O2
to H2O
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Tetrameric hemoprotein present in peroxisomes
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Glutathione peroxidase (GSH.Px)
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Removes H2O2 and
lipid peroxides
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Selenoproteins (contains Se2+)
Primarily in the cytosol also mitochondria
Uses GSH
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Vitamins
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Alpha tocopherol
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Breaks lipid peroxidation
Lipid peroxide and O2·⁻
and ·OH scavenger
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Fat soluble vitamin
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Beta carotene
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Scavenges ·OH, O2·⁻
and peroxy radicals
Prevents oxidation of vitamin A
Binds to transition metals
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Fat soluble vitamin
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Ascorbic acid
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Directly scavenges O2·⁻,
·OH, and H2O2
Neutralizes oxidants from stimulated
neutrophils
Contributes to regeneration of vitamin
E
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Water soluble vitamin
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-Modified from Fisher, 1988.
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